Marsdenia goromotoorum Gâteblé, Fleurot, Meve & Liede, 2019

Gâteblé, Gildas, Fleurot, Dominique, Meve, Ulrich & Liede-Schumann, Sigrid, 2019, An unorthodox, new endemic species in New Caledonian Marsdenia (Apocynaceae, Asclepiadoideae, Marsdenieae), Phytotaxa 405 (3), pp. 121-126 : 122-125

Marsdenia goromotoorum Gâteblé, Fleurot, Meve & Liede , sp. nov. ( Figs. 1 , 2 , 3 )

Diagnosis: — Marsdenia goromotoorum is most similar to M. neomicrostoma Meve et al. (2018: 208) but differs greatly from the latter by having pinkish-red and smaller flowers (3–4 mm long) vs. whitish flowers (4–6 mm long), by the absence of gynostegial corona vs. presence of gynostegial corona, and by its ovate-elliptic and tomentose leaves vs. linear and glabrous leaves.

Type:— NEW CALEDONIA. Pouembout , Kopéto, elev. 180 m, 21°11’52.243’’S, 165°01’58.984’’E, 15 January 2019, D. Fleurot & J.- F. Porin-Pouéa 539 (holotype P; isotypes NOU [ NOU090278 , NOU090301 ]) .

Plants suffrutescent, ascending, twining 0.25 to 1.5 m high, up to 1 cm in diameter at the base, not epiphytic, sparsely branched, stem base suberose. Shoots semi - perennial, herbaceous, tomentose with 0.2–0.35 mm long trichomes; internodes 1–5 cm long, 2–3 mm diam., without adventitious roots. Latex clear, scarce. Leaves opposite; petiole 5–13 × ca. 1 mm, tomentose all over with ca. 0.2 mm long trichomes; blade without visible colleters at base, 2–2.7 × 1.2–1.7 cm, flat, ovate to elliptic, apex mucronate, mucro about 0.5 mm long; base rounded to truncate, margin entire, slightly revolute on dry material, not so on fresh one, chartaceous to coriaceous, both surfaces with scattered, erect, 80–160 μm long, whitish trichomes, trichomes longer and denser on the abaxial surface, discolorous, adaxially green, abaxially light green; venation brochidodromous, with 3–4 pairs of secondary veins easily seen on both fresh and dry materials on the abaxial surface. Inflorescences extra-axillary, condensed, sciadioidal racemes, 5–35 flowered, 1–10 flowers open at a time, very slightly sweetish scented. Peduncles 2–3 × ca. 1 mm, tomentose with ca. 0.2 mm long trichomes. Flowers with floral bracts ca. 0.6 × 0.4 mm, triangular, densely covered with trichomes, persistent. Pedicels 2–4 × ca. 1 mm, dark red, tomentose with ca. 0.2 mm long trichomes. Floral buds 2–3 × 1–1.5 mm, cylindrical. Calyx with 1–2 calycine colleters in sepal sinuses, sepals quincuncial, 1.3 × 1 mm, broadly ovate with round apex, brownish-red, ciliate, abaxially densely pubescent, especially in the central part and flanked with more or less glabrous sides. Corolla tubular to narrowly urceolate, slightly fleshy, glabrous and pinkish-red on the outer surface, pale pink on the inner surface; tube ca. 2.5–3 × 1.5–2 mm, adaxial corolla surface with two broad rings of trichomes, an upper one consisting of long antrorse, white trichomes on the basal halves of the corolla lobes and mouth of the tube, forming a cone of trichomes closing the corolla throat and hiding the gynostegium, a lower one consisting of scattered, horizontally spreading white trichomes surrounding the gynostegium; corolla lobes valvate in bud, lobes up to ca. 1 × 1 mm, triangular to broadly ovate, bent upward at anthesis, margins thin, even. Corolline and gynostegial corona absent. Gynostegium subsessile, conical, ca. 1.5 × 1.3 mm, filament tube basally with wing-like extensions; anther wings (guide rails) ca. 300 μm long, consisting of distal and proximal ridge, oblique to 25°; connective appendages ca. 500 × 300 μm, lanceolate, narrower than the stamen, connivent-erect and appressed to style-head. Pollinarium: corpusculum ca. 175 × ca. 70 μm, oblong; caudicles ca. 150 x 30 μm, basally inserted at the corpusculum, bent upwards, linear, broadened at both ends; pollinia basally attached to the caudicles, erect, ca. 220 × 100 μm, ellipsoid, narrowly elliptic in cross-section. Style-head ca. 0.75 × 0.7 mm diam., upper part ca. 0.35 mm long, conical. Follicles one or two per flower, erect, 40–70 × ca. 2 mm when dry, ca. 3–4 mm wide in fresh material, subcylindrical to slightly obclavate, round in cross-section, smooth, densely tomentose pubescent, apex obtuse, very slightly beaked; seeds ca. 5–6 × 1.8–2 mm, oblanceolate in outline, marginally with 0.5–1 mm wide wing with entire margin; coma up to 18 mm long, white.

Phenology: —Flowering in December–March, fruiting in December–April.

Distribution and habitat:— New Caledonia, narrow endemic to the base of the Kopéto massif south of Pouembout. The species grows in a maquis formation of Gymnostoma Johnson (1980: 83) , associated with species of Alyxia Brown (1810: 469) , Bocquillonia Baillon (1862: 225) , Hibbertia Andrews (1800: 126) , Scaevola Linnaeus (1771: 145) , Tetraria Palisot de Beauvois (1816: 54) and Thiollierea , on serpentine (ultramafic) substrate. Elevation: 180 m.

Etymology:—The name refers to the Goromoto, a clan of the Ouaté tribe which is part of the Poindah custom district and of the larger custom area of Paici-Cemuhi. The Goromoto clan is from the Baï family whereas the Naouna clan is part of the Doui family, also from the Ouaté tribal village. A new micro-endemic species from the same place is currently being described for the Naouna clan in Thiollierea (Fleurot & Barrabé, in prep.). The place, southern base of the Kopéto massif, where these two new species are growing is a culturally important and sacred place because it used to be a cemetery site where the two clans used to inhume their deceased members.

Conservation status:—The micro-endemic Marsdenia goromotoorum is restricted to the base of the Kopéto nickel mining site. It is currently not threatened by open nickel mining as the serpentines where it grows have a low nickel content. The main threat to the species is the anthropogenic fires that frequently occur in the Ouaté area. However, the place is not accessible to the public because it is part of the Société Le Nickel restricted access mining site and fires are not likely to occur in the area. The species seems very rare in the locality with only eight plants (five fertile) seen on a 30 m ² area. Considering the potential impact of a big fire event, the proposed provisional IUCN Status is “Critically Endangered” using Red List criteria (IUCN 2017) under the criterion CRD.

Notes: —Initially, we believed that this unorthodox new species could belong to the genus Dischidia (tribe Marsdenieae ) where similarly looking and sized, tubular and red flowers occur, e.g., Dischidia vidalii Beccari (1886: 272) (syn. D. pectenoides Pearson, 1902: 377 ). However, the new species is not leaf-succulent, lives not as epiphyte (like typical Dischidia ) but is an erect, twining plant which develops woody and suberose basal stems of up to one cm in diameter. Especially in Australasia and New Caledonia, and even on a world-wide scale, such growth-forms are often found in Marsdenia (cf. Forster 1995). However, we failed to pinpoint a particular species as closest relative when considering all flower details. In vegetative habit instead, leaf shape of the new species and its small cylindricalobclavate follicles with oblanceolate smooth seeds with entire margins can be seen also in Gymnema , another Old World Marsdenieae genus which is best characterized by the possession of a corolline corona ( Endress et al. 2018)— but this is missing here. Comparing pollinarium morphology it is nevertheless Gymnema tricholepis Schlechter (1908: 17) which shows highly similar pollinaria to M. goromotoorum ( Fig. 1F ). Molecularly (Liede-Schumann et al., unpubl. phylogeny), the new species shares a clade with a number of New Caledonian Marsdenia species that typically have urceolate to tubular corollas. In this phylogeny, M. goromotoorum is sister to a group of species encompassing M. ericoides Schlechter (1906: 246) , M. assimulata Moore (1921: 367) , and M. mackeeorum Meve et al. (2017: 60) . All these are only found on ultramafic substrates like the new species. Clear instead of milky latex occurs also in M. ericoides , whereas M. assimulata and M. mackeeorum have milky latex.The flowers of the new species are most similar to those of Marsdenia neomicrostoma , however this species is retrieved in another Australian/New Caledonian subclade. Marsdenia neomicrostoma shares a (urceolate-)tubular corolla tube, and the erect to apically connivent, subcircular corolla lobes that limit the access to the corolla tube (and gynostegium). Similar flowers (although more pronouncedly urceolate and whitish-green) are also found in Australian members of the same subclade in case of Marsdenia australis ( Brown 1849: 81) Druce (1917: 634) . The latter species shares the possession of a gynostegial corona and linear leaves with M. neomicrostoma , whereas the lack of corona lobes is a unique feature of M. goromotoorum .

The pollination system of M. goromotoorum is unknown though two attempts to record flower visitors were performed using camera traps and observations. However, the pollination strategy appears to be efficient as we spotted one flower with a pollinium fixed at mouth of a guide-rail, and with pollen tubes germinated (from base of pollinium). The many follicles produced in habitat are proof of successful reproduction ( Fig. 1A, C, G ). Corolla size, shape, structure (=corolla tubular and of limited access) and coloration, and a light flower scent, point to (smaller) Lepidoptera as possible pollinators (cf. Proctor et al. 1996).

Figures

FIGURE 1. Marsdenia goromotoorum. A. An adult plant growing in its serpentine maquis habitat at the type locality (15th of January 2019); B. Flowering twig; C. A fertile branch with both flowers and follicles; D. Detail of an especially rich inflorescence; E. Flower in lateral view with parts cut away to show the two rings of trichomes inside corolla, and the gynostegium; F. Pollinarium; G. Two follicles. A, D Fleurot 538; B, E Fleurot 539; C, F, G Fleurot 506. Photos:A–D, G: D. Fleurot, E: G. Gâteblé, F: U. Meve.

FIGURE 2. Marsdenia goromotoorum. A. Longitudinal cut flower; B. Gynostegium in lateral view (lanceolate connective appendages hide the style-head); C. Pollinarium in frontal view with caudicles slightly recurved after removal from the style-head; D. Same pollinarium as in C in lateral back view.All from Fleurot 506 (Drawn by U. Meve).

FIGURE 3. Distribution map of Marsdenia goromotoorum (star) in New Caledonia with an insert showing the Kopéto massif area. Ultramafic substrates are shown in orange.